Will drought evolution accelerate under future climate?

The evolution speed of droughts largely determines their characteristics and ensuing implications. Despite its importance, the potential accelerating effects of future climate change on these events are not fully understood. Here, we assessed changes in instantaneous development speed (IDS) and instantaneous recovery speed (IRS) of global droughts at various warming levels (1.5 °C, 2 °C, and 3 °C) under two Shared Socio-economic Pathways (SSP2.4–5 and SSP5.8–5 scenarios). The recently released NASA Earth Exchange Global Daily Downscaled Projections CMIP6 datasets were used to characterize droughts based on the standardized precipitation index and run theory. In SSP2.4–5 and SSP5.8–5 scenarios, the proportions of global regions that underwent faster IDS accounted for 69.5 % vs. 43.3 %, and the slower counterparts were 29.4 % vs. 55.7 % compared to the historical period (1950–2014). In contrast, the global IRS in both SSP scenarios mainly slowed down, especially the SSP 5.8–5 scenario exhibiting declines in 75 % of the global regions. With intensified global warming, the regions with rapid IDS and IRS would expand, while low-IRS areas would shrink. Notably, areas showing slower IDS also increased when the warming level rose from 1 °C to 3 °C. Furthermore, eight hotspots with relatively rapid historical IDS and IRS persisted across the three warming levels under the SSPs in different future trends compared to the past conditions. These results provide insights into drought evolution speed assessment under climate change, highlighting the necessity of considering this variable in developing effective response strategies.

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